7 Answers
7

fill any holes and cracks with suitable filler, possibly using flexible filler for cracks.

sand and prime the filled areas - priming will seal the filler and keep it in place. You might want to sand and reprime the whole wall to avoid a patchy look.

repaint the wall with at least two coats of your new colour.

If the cracks are large you might want to check there's no current problem. New houses will settle quite a bit when first built and there'll even be some movement in older homes.

If you are painting over a dark colour with a light colour you might need more than 2 coats to stop the previous colour showing through. If that's the case then using a primer or basic white matt emulsion for the first coat (or two if it's really dark) is a more cost effective option than using the more expensive coloured paint for all the coats. Unfortunately you don't always find that out in time.

Paint in full daylight - especially for the final coat - so you can see where you've been and be methodical.

If you fill holes/repair cracks, it's a good idea to prime the entire wall (not just patches). If you only prime the patched areas, you could end up with a splotchy looking finish.
–
Tester101♦Feb 8 '12 at 17:16

1

A tinted primer when going from light to dark paint also seems to help. We put a thick forest green type color over a pale yellow in two rooms. The first was just painted over, took 4 coats! The second with a tinted primer coat took just 2 coats of paint.
–
Steve JacksonFeb 8 '12 at 18:29

1

If there are stains on the wall, or if you're painting over a dark coloured paint it's best to prime the walls with a pigmented sealer/stain blocker undercoat first. This stops the existing paint showing through and means you will use less topcoat to get a good consistent colour.
–
MattJul 28 '13 at 20:57

There's one tip that was completely missed, and should have been at the start:

When painting over a surface that has had to be repaired or was very dirty (scrub it clean first), get both the paint and the primer tinted to the same color. As long as you buy the paint/primer in the same brand and they are both the same base, you will have exact match.

This one tiny little tip guarantees a perfect job with only one coat of primer and one coat of paint.

Priming is best. If you have to do two coats of paint to cover the old color, why not use a good primer or primer/sealer and one coat of a good paint? Most people will say otherwise, but primer will stick to old paint a lot better than new paint will.

I recommend wiping the walls down with a damp cloth first, but it's a lot of work, and I've never done it to a wall that wasnt't obviously filthy.

The problem is that one coat of the good paint may not be enough: the primer may shine through.
–
Vebjorn LjosaAug 23 '10 at 18:26

2

Perhaps. Primer is usually clear or white. If it's white, a light color shouldn't give you any trouble. If the paint is decent, a dark color should be able to cover it as well. I guess the success depends on the paint color and quality. Worst-case, you need a second coat of paint- but many times, you won't.
–
nstenzAug 24 '10 at 20:32

At Home Depot I always have them tint the primer the same color as the paint. They do that at no cost. Also after caulking or drywall repair is dry I paint those areas with one coat of paint or primer before starting on trim cut in work . When I paint body .It is dry. The paint is always blotchy if those areas haven't had an extra coat.

I painted a light yellow over a dark blue wall. I used Behr paint with primer added. After two coats the blue still showed through. Not sure if prior priming was necessary since paint contained it already. One of the walls was already white and one coat covered it up.